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Topic: Melting points of alcohols  (Read 15179 times)

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Offline Jim42

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Melting points of alcohols
« on: October 18, 2007, 05:17:44 PM »
why is the melting point of 1-butanol higher than that of 1-propanol?
I realize that the longer your carbon chain the more intermolecular forces will be present and therefor you will have higher melting points. But my question is how can I explain this trend in melting points of these 5 primary alcohols

methanol -93.9
ethanol -117.3
1-propanol -126.5
1-butanol -89.53
1-pentanol -79
all temperatures are in degrees celcius i have looked at what  could happen with the hydrogen bonding and could not find anything. I'm wondering why from methanol to 1-propanol they require less and less energy to break the bonds and then 1-butanol and 1-pentanol require more energy. The pattern does not make sense to me.
« Last Edit: October 18, 2007, 08:33:43 PM by Jim42 »

Offline DevaDevil

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Re: Melting points of alcohols
« Reply #1 on: October 18, 2007, 06:06:34 PM »
longer hydrocarbon chain means higher van der Waals forces, aka higher melting point

Offline Jim42

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Re: Melting points of alcohols
« Reply #2 on: October 18, 2007, 11:23:12 PM »
Thanks for the comment on Van der Wal forces. By that logic though it would seem to me that menthanol and ethanol with shorter chains should have lower melting point?

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